A conventional GPS features an antenna for receiving GPS signals from orbiting satellites and a chipset that processes these signals to calculate a GPS ‘fix’ featuring GPS data such as latitude, longitude, altitude, heading, and velocity. The latitude, longitude, and altitude describe the vehicle's location with a typical accuracy of about 10 meters or better.
Conventional GPSs can be combined with systems for collecting diagnostic data from the vehicle to form ‘telematics’ systems. Such diagnostic data is typically collected from OBD-II systems mandated by the Environmental Protection Agency (EPA) for monitoring light-duty automobiles and trucks beginning with model year 1996. OBD-II systems monitor the vehicle's electrical, mechanical, and emissions systems and generate data that are processed by a vehicle's engine control unit (ECU) to detect malfunctions or deterioration in the vehicle's performance. The data typically include parameters such as vehicle speed (VSS), engine speed (RPM), engine load (LOAD), and mass air flow (MAF). The ECU can also generate diagnostic trouble codes (DTCs), which are 5-digit codes (e.g., ‘P0001’) indicating electrical/mechanical problems with the vehicle. DTCs and other diagnostic data are made available through a standardized, serial 16-cavity connector referred to herein as an ‘OBD-II connector’. The OBD-II connector is in electrical communication with the vehicle's ECU and typically lies underneath the vehicle's dashboard.
U.S. Pat. Nos. 6,064,970, 6,236,933, and 6,295,492, for example, describe in-vehicle systems that collect both GPS data and diagnostic data from the vehicle's OBD-II systems. The in-vehicle systems then transmit these data using wireless means to a host computer system.